JP4672554B2 - Method for producing aliphatic polyester - Google Patents

Abstract

An aliphatic polyester improved provided by using water positively as an initiator or/and a molecular weight-adjusting agent, is improved in moisture resistance. More specifically, a cyclic ester containing proton-source compounds including more than 80 ppm of water as an initiator or/and a molecular weight-adjusting agent, is subjected to ring-opening polymerization, and the resultant aliphatic polyester is compounded with a carboxyl group-capping agent to produce such an aliphatic polyester.

Description

  The present invention relates to a method for producing an aliphatic polyester such as polyglycolic acid by ring-opening polymerization of a cyclic ester such as glycolide, and more specifically, water is actively used as an initiator or / and a molecular weight regulator. The present invention relates to an improvement in a method for producing an aliphatic polyester by ring-opening polymerization of a cyclic ester.

  Aliphatic polyesters such as polyglycolic acid and polylactic acid have been attracting attention as biodegradable polymer materials that have a low environmental impact because they are decomposed by microorganisms or enzymes existing in nature such as soil and sea. In addition, since aliphatic polyester has biodegradable absorbability, it is also used as a medical polymer material such as surgical sutures and artificial skin.

  Among aliphatic polyesters, polyglycolic acid is excellent in gas barrier properties such as oxygen gas barrier properties, carbon dioxide gas barrier properties, and water vapor barrier properties, and is excellent in heat resistance and mechanical strength. Or, it is being used in combination with other resin materials.

  Aliphatic polyesters can be synthesized, for example, by dehydration polycondensation of α-hydroxycarboxylic acids such as glycolic acid and lactic acid. In order to efficiently synthesize high-molecular weight aliphatic polyesters, in general, α-hydroxycarboxylic acid is used. A method of synthesizing a bimolecular cyclic ester of an acid and subjecting the cyclic ester to ring-opening polymerization is employed. For example, polyglycolic acid is obtained by ring-opening polymerization of glycolide, which is a bimolecular cyclic ester of glycolic acid. Polylactic acid is obtained by ring-opening polymerization of lactide, which is a bimolecular cyclic ester of lactic acid.

  The cyclic ester generally contains impurities such as free carboxylic acid compounds such as α-hydroxycarboxylic acid and linear α-hydroxycarboxylic acid oligomers used as raw materials, and water. Impurities such as water adversely affect the ring-opening polymerization of cyclic esters even in trace amounts, and it has been proposed to use high-purity cyclic esters with impurities removed as much as possible during ring-opening polymerization. .

  On the other hand, in order to control the molecular weight of the aliphatic polyester, alcohols such as higher alcohols are used as molecular weight modifiers in the ring-opening polymerization of the cyclic ester. A method of determining the amount of alcohol to be added based on the amount of free carboxylic acid compound contained in the cyclic ester has also been proposed.

  For example, conventionally, when ring-opening polymerization of glycolide, a method of using substantially pure glycolide purified by recrystallization or the like and using a higher alcohol such as lauryl alcohol as a molecular weight modifier has been adopted ( For example, see the following Patent Document 1.)

  In addition, a purification method for removing impurities such as water from the cyclic ester has been proposed (see, for example, Patent Document 2 below). In this document, impurities such as water, α-hydroxycarboxylic acid and low molecular weight oligomers contained in cyclic esters exert various actions such as initiators, chain transfer agents, catalyst deactivators, etc. It has been pointed out that these impurities should be removed because they inhibit ring polymerization.

  There has been proposed a method for producing an aliphatic polyester by ring-opening polymerization of a cyclic ester having a water content of 80 ppm or less and an acid value of 0.10 mgKOH / g or less (see, for example, Patent Document 3 below). In this document, if the amount of water in the cyclic ester is reduced, the polymerization rate is increased to obtain a high molecular weight polymer, and if alcohol is present in the polymerization system, the action of moisture is suppressed. It is described that a high-quality aliphatic polyester can be produced.

  A method for producing an aliphatic polyester by ring-opening polymerization of a cyclic ester, wherein the amount of a hydroxyl compound added to a reaction system is determined based on the amount of a free carboxylic acid compound contained in the cyclic ester A method has been proposed (see, for example, Patent Document 4 below). In this document, α-hydroxycarboxylic acid and linear α-hydroxycarboxylic acid oligomer used in the production of the cyclic ester are shown as the free carboxylic acid compound, and the hydroxyl group compound has 12 to 18 carbon atoms. It is stated that monovalent linear saturated aliphatic alcohols are preferred.

  In this document, when impurities such as moisture and free carboxylic acid compounds are contained in the cyclic ester, the polymerization reaction is adversely affected, and the targeting of producing a polymer with a targeted molecular weight even under the same polymerization conditions. It is pointed out that it is impossible. In this document, since the control of the molecular weight of the aliphatic polyester tends to be difficult when the water content is large, the water content in the cyclic ester is preferably 100 ppm or less in order to control the molecular weight with high accuracy. It is described.

  Furthermore, in this document, it is easy to remove the water in the cyclic ester in the purification / drying step immediately before the polymerization, but the free carboxylic acid compound is difficult to remove and gives it to the polymerization reaction. It has been pointed out that the influence is great, and the cyclic ester is opened by a very small amount of water during storage, so that a new free carboxylic acid compound is easily generated. In this document, a method for producing an aliphatic polyester having a target molecular weight by quantifying a free carboxylic acid compound contained in a cyclic ester and adding an appropriate amount of a hydroxyl compound (for example, a higher alcohol). Has been proposed.

US Pat. No. 3,442,871 JP-A-8-301864 JP-A-10-158371 Japanese Patent No. 3075665 JP 2001-261797 A

  As described above, conventionally, it has been considered necessary to remove water as much as possible as an impurity that inhibits the ring-opening polymerization of a cyclic ester. However, water is the most universal compound existing in nature, and there are limits to eliminating it as an impurity. As a result of detailed studies on the role of water in the ring-opening polymerization system of cyclic esters, the present inventors have used a proton source compound containing water as a molecular weight regulator to control the total proton concentration in the cyclic ester. It has been found that the ring-opening polymerization of a cyclic ester proceeds smoothly and the molecular weight of the resulting aliphatic polyester can be controlled, and based on this finding, a method for producing an aliphatic polyester has already been proposed (WO 2004/033527). Publication).

The main object of the present invention is to improve the above-described method for producing an aliphatic polyester.
That is, according to the study of the present inventors, the above-described method for producing an aliphatic polyester has a problem with water resistance, and the present invention aims to provide a method for producing an aliphatic polyester with improved water resistance. To do.

  According to the study by the present inventors, the reason why the water resistance of the produced aliphatic polyester in the above-described method for producing an aliphatic polyester is low is the presence of a carboxyl group in the produced aliphatic polyester. This problem is solved by blending the sealant.

That is, in the method for producing an aliphatic polyester of the present invention, an aliphatic polyester having a controlled molecular weight is produced using a moisture-containing proton source compound as an initiator or / and a molecular weight regulator, and the carboxyl group is sealed. It is intended to improve water resistance. More specifically, the present invention relates to a cyclic ester comprising a proton source compound containing more than 80 ppm of water as an initiator or / and a molecular weight regulator , water in the cyclic ester and free α- corresponding to the cyclic ester. In order to obtain an aliphatic polyester having a desired molecular weight by changing the water content so that the total proton concentration including hydroxycarboxylic acid and its dimer is in the range of more than 0.09 mol% and less than 2.0 mol% The present invention provides a method for producing an aliphatic polyester, which comprises ring-opening polymerization and blending a carboxyl group-blocking agent with the resulting aliphatic polyester.

The data plot which shows the correlation with the weight average heavy molecular weight (Mw) of the aliphatic polyester obtained by the manufacturing method of this invention, and the total proton concentration in cyclic ester is shown. The data plot which shows the correlation with the melt viscosity of the aliphatic polyester obtained by the manufacturing method of this invention and the total proton concentration in cyclic ester is shown.

  The method for producing an aliphatic polyester according to the present invention is simply described by blending a carboxyl group-blocking agent with the aliphatic polyester produced in the above-mentioned invention of WO 2004/033527 (hereinafter referred to as “prior invention”). It is characterized by this. Hereafter, the manufacturing method of the aliphatic polyester of this invention is demonstrated along description of prior invention.

[1. Cyclic ester]
As the cyclic ester used in the present invention, a bimolecular cyclic ester, lactone and cyclic ether ester of α-hydroxycarboxylic acid are preferable. Examples of the α-hydroxycarboxylic acid forming the bimolecular cyclic ester include glycolic acid, L- and / or D-lactic acid, α-hydroxybutyric acid, α-hydroxyisobutyric acid, α-hydroxyvaleric acid, α-hydroxy. Examples include caproic acid, α-hydroxyisocaproic acid, α-hydroxyheptanoic acid, α-hydroxyoctanoic acid, α-hydroxydecanoic acid, α-hydroxymyristic acid, α-hydroxystearic acid, and alkyl-substituted products thereof. Can do.

  Examples of the lactone include β-propiolactone, β-butyrolactone, pivalolactone, γ-butyrolactone, δ-valerolactone, β-methyl-δ-valerolactone, and ε-caprolactone. Examples of the cyclic ether ester include dioxanone.

  The cyclic ester having an asymmetric carbon may be any of D-form, L-form, meso-form and racemic form. These cyclic esters can be used alone or in combination of two or more. When two or more cyclic esters are used, any aliphatic copolyester can be obtained. The cyclic ester can be copolymerized with other copolymerizable comonomers, if desired. Examples of other comonomers include cyclic monomers such as trimethylene carbonate and 1,3-dioxane.

  Among the cyclic esters, glycolide which is a bimolecular cyclic ester of glycolic acid, L- and / or D-lactide which is a bimolecular cyclic ester of L- and / or D-lactic acid, and a mixture thereof are preferred, and glycolide Is more preferable. Glycolide can be used alone, but it can also be used in combination with other cyclic monomers to produce a polyglycolic acid copolymer (copolyester). When producing a polyglycolic acid copolymer, the copolymerization ratio of glycolide is preferably 60% by weight, more preferably 70% by weight or more, particularly from the viewpoint of physical properties such as crystallinity and gas barrier properties of the resulting copolyester. Preferably it is 80% by weight or more. The cyclic monomer copolymerized with glycolide is preferably lactide, ε-caprolactone, dioxanone, or trimethylene carbonate.

  The manufacturing method of cyclic ester is not specifically limited. For example, glycolide can be obtained by a method of depolymerizing glycolic acid oligomers. Examples of the depolymerization method of glycolic acid oligomer include, for example, a melt depolymerization method described in US Pat. No. 2,668,162, a solid-phase depolymerization method described in JP-A No. 2000-119269, The solution phase depolymerization method described in Japanese Patent No. 328881 and International Publication No. 02 / 14303A1 pamphlet can be employed. K. Glycolide obtained as a cyclic condensate of chloroacetate as reported in Chujo et al., Die Makromolekule Cheme, 100 (1967), 262-266 can also be used.

  In order to obtain glycolide, the solution phase depolymerization method is preferable among the above depolymerization methods. In the solution phase depolymerization method, (1) a mixture containing a glycolic acid oligomer and at least one high-boiling polar organic solvent having a boiling point in the range of 230 to 450 ° C. is subjected to decomposition of the oligomer under normal pressure or reduced pressure. (2) the oligomer is dissolved in the solvent until the residual ratio (volume ratio) of the melt phase of the oligomer is 0.5 or less, and (3) further at the same temperature. The oligomer is depolymerized by continuing heating, and (4) the produced dimer cyclic ester (that is, glycolide) is distilled together with a high-boiling polar organic solvent, and (5) glycolide is recovered from the distillate.

  Examples of the high boiling polar organic solvent include bis (alkoxyalkyl esters) phthalates such as di (2-methoxyethyl) phthalate, alkylene glycol dibenzoates such as diethylene glycol dibenzoate, and aromatic carboxyls such as benzylbutyl phthalate and dibutyl phthalate. Examples include acid esters, aromatic phosphate esters such as tricresyl phosphate, polyalkylene glycol ethers such as polyethylene dialkyl ether, etc., and usually 0.3 to 50 times (weight ratio) with respect to the oligomer. Use at a rate of. Along with the high-boiling polar organic solvent, polypropylene glycol, polyethylene glycol, tetraethylene glycol or the like can be used in combination as a solubilizer for the oligomer, if necessary. The depolymerization temperature of the glycolic acid oligomer is usually 230 ° C. or higher, preferably 230 to 320 ° C. Depolymerization is carried out under normal pressure or reduced pressure, but it is preferable to depolymerize by heating under reduced pressure of 0.1 to 90.0 kPa (1 to 900 mbar).

  As the cyclic ester, it is preferable to use a purified cyclic ester having a moisture content of 60 ppm (weight basis) or less, preferably 50 ppm or less, more preferably 40 ppm or less. If the initial moisture content in the cyclic ester used is too high, the range of the molecular weight of the produced aliphatic polyester that can be controlled by adding water as a molecular weight modifier is suppressed.

  The content of the hydroxycarboxylic acid compound contained as an impurity in the cyclic ester is preferably as low as possible. The content of α-hydroxycarboxylic acid in the cyclic ester is preferably 200 ppm (weight basis) or less, more preferably 150 ppm or less, still more preferably 130 ppm or less, and particularly preferably 100 ppm or less.

  The cyclic ester usually contains a linear α-hydroxycarboxylic acid oligomer. This oligomer is mostly a linear α-hydroxycarboxylic acid dimer. The content of the linear α-hydroxycarboxylic acid oligomer in the cyclic ester is preferably 2,000 ppm or less, more preferably 1,500 ppm or less, still more preferably 1,200 ppm or less, and particularly preferably 1,000 ppm or less. is there.

  Cyclic esters such as glycolide and lactide contain α-hydroxycarboxylic acid and linear α-hydroxycarboxylic acid oligomers by hydrolysis and polymerization during storage due to a small amount of moisture contained as impurities. The rate shows an upward trend. Therefore, the cyclic ester immediately after purification desirably has a moisture content of 50 ppm or less, an α-hydroxycarboxylic acid content of 100 ppm, and a linear α-hydroxycarboxylic acid oligomer content of 1,000 ppm or less. In addition, refinement | purification of cyclic ester can be performed by combining the recrystallization process, drying process, etc. of a crude cyclic ester according to a conventional method.

[2. Method for producing aliphatic polyester]
In order to produce an aliphatic polyester using a cyclic ester, it is preferable to employ a method in which the cyclic ester is heated to cause ring-opening polymerization. This ring-opening polymerization method is a substantially ring-opening polymerization method. The ring-opening polymerization is usually performed in the presence of a catalyst at a temperature in the range of 100 to 270 ° C, preferably 120 to 260 ° C.

  The catalyst is not particularly limited as long as it is used as a ring-opening polymerization catalyst for various cyclic esters. Specific examples of such a catalyst include oxides and chlorides of metal compounds such as tin (Sn), titanium (Ti), aluminum (Al), antimony (Sb), zirconium (Zr), and zinc (Zn). , Carboxylates, alkoxides and the like. More specifically, preferable catalysts include, for example, tin such as tin halide (for example, tin dichloride and tin tetrachloride), and organic carboxylate (for example, tin octoate such as tin 2-ethylhexanoate). Examples thereof include, but are not limited to, titanium compounds such as alkoxy titanates; aluminum compounds such as alkoxyaluminum; zirconium compounds such as zirconium acetylacetone; and antimony halides.

  In general, the amount of the catalyst used may be small relative to the cyclic ester, and is usually selected from the range of 0.0001 to 0.5% by weight, preferably 0.001 to 0.1% by weight, based on the cyclic ester. Is done.

  In the present invention, prior to ring-opening polymerization, the content of moisture and hydroxycarboxylic acid compound contained as impurities in the cyclic ester is measured, and based on the respective contents, the total proton amount of impurities is calculated, The water content in the cyclic ester is set so as to exceed 80 ppm, and moreover exceed 100 ppm. The water content in the cyclic ester is measured using a Karl Fischer moisture meter. The α-hydroxycarboxylic acid and the linear α-hydroxycarboxylic acid oligomer contained in the cyclic ester are quantified by gas chromatography analysis or the like after converting each carboxyl group to an alkyl ester group.

  The total proton concentration of impurities contained in the cyclic ester is calculated based on the total amount of the hydroxycarboxylic acid compound and moisture contained as impurities in the cyclic ester. For example, in the case of glycolide, a trace amount of water and a hydroxycarboxylic acid compound composed of glycolic acid and a linear glycolic acid oligomer are contained as impurities. Most of the linear glycolic acid oligomers contained in the purified glycolide are glycolic acid dimers. In the case of lactide, moisture, lactic acid, and linear lactic acid oligomer are contained as impurities. The proton concentration (mol%) based on these hydroxycarboxylic acid compounds is calculated based on the content, molecular weight, and number of hydroxyl groups (usually one). The proton concentration (mol%) of water is calculated based on the water content and molecular weight. The proton concentration is calculated as mol% based on the total amount of cyclic ester and impurities.

  The total proton concentration of impurities contained in the cyclic ester is preferably 0.01 to 0.5 mol%, more preferably 0.02 to 0.4 mol%, particularly preferably 0.03 to 0.35 mol%. It is. The impurity total proton concentration is limited in reducing the hydroxycarboxylic acid compound by purification, and it is difficult to make it extremely low. If the total impurity proton concentration is too high, it becomes difficult to accurately control the melt viscosity, molecular weight, etc. by adding water.

In the present invention, the molecular weight of the resulting aliphatic polyester is controlled by adjusting the total proton concentration in the cyclic ester by adding water to a purified cyclic ester having a water content of 60 ppm or less. Water is added to the purified cyclic ester so that the total proton concentration in the cyclic ester is preferably in the range of more than 0.09 mol% and less than 2.0 mol%, more preferably in the range of 0.1 to 1.0 mol%. adjust.
Based on the molecular weight of the produced aliphatic polyester, it is possible to predict the setting of molding conditions and the mechanical strength, yellowness, etc. of the molded product.

  When ring-opening polymerization is performed without adding water to the purified cyclic ester, unreacted monomers are likely to remain in the produced polymer. When the content of the volatile component containing the residual monomer as a main component increases, in addition to the deterioration of the quality of the polymer, the melt viscosity decreases and the yellowness increases. It is difficult to control the polymer melt viscosity and the like only by controlling the degree of purification of the cyclic ester.

  When water is added to the purified cyclic ester to adjust the total proton concentration in the cyclic ester, physical properties such as melt viscosity, molecular weight, and yellowness of the produced polymer can be accurately controlled. When water is used as a molecular weight regulator, the reaction efficiency of ring-opening polymerization is high, and the content of volatile components mainly composed of residual monomers can be significantly reduced. That is, when water is used as the molecular weight regulator, a polymer having a high molecular weight and a high melt viscosity can be synthesized. When the total proton concentration in the cyclic ester is changed by adding water, the melt viscosity and molecular weight of the produced polymer can be controlled within a desired range while keeping the amount of volatile matter (residual monomer) at a low level. As a result, there is a close correlation between the total proton concentration in the cyclic ester and the melt viscosity and molecular weight of the polymer.

  Specifically, the same polymerization conditions (reaction vessel, polymerization temperature, polymerization time, type of monomer and degree of purification, etc.) were used except that the amount of water added was changed to change the total proton concentration in the cyclic ester. The correlation as described above can be clarified using the results of the measurement of the melt viscosity, molecular weight, and yellowness of the resulting aliphatic polyester as a database.

  For example, when water is added to glycolide to change the total proton concentration, and the melt viscosity, weight average molecular weight, and yellowness of polyglycolic acid obtained by ring-opening polymerization of glycolide are measured, these physical properties and It was found that there was a relationship between the total proton concentration.

  For example, FIG. 1 shows a plot of the relationship between the weight-average molecular weight (Mw) of the resulting aliphatic polyester obtained by changing the amount of water added and the total proton concentration (the results of the prior invention examples are indicated by “●”). Inventive Example results are indicated by “Δ”).

An example of regression analysis based on a database will be described. The total proton concentration (x) of glycolide is used as an independent variable (explanatory variable), and the melt viscosity (y) of polyglycolic acid is used as a dependent variable (explained variable). As a result of regression analysis, it was found that a relational expression of a linear model, a log-log model, and a semi-log model was established between them. Among these, the following formula (1)
y = a · b ^x (1)
(A and b are parameters.)

It was found that the relational expression of the semilogarithmic model represented by (2) has the highest multiple correlation R and multiple determination R2. FIG. 2 shows a correlation data plot between the melt viscosity and the total proton concentration including the correlation curve thus obtained.

  In addition, when the amount of water added is increased and the total proton concentration in the cyclic ester is increased, the melt viscosity and molecular weight of the produced polymer decrease, but the yellowness (Yellow Index; YI) is reversed. It has been found that the color becomes smaller in proportion and the degree of coloring is improved. Therefore, by adjusting the total proton concentration of the cyclic ester by adding water, an aliphatic polyester having a low melt viscosity and a small yellowness suitable for injection molding can be produced. By using water as a molecular weight regulator in this way, the coloration of the polymer can be suppressed, so that an increase in coloration due to the incorporation of a carboxyl group blocking agent can be suppressed and balanced with an improvement in water resistance. it can.

  The ring-opening polymerization of the cyclic ester may be carried out using a polymerization vessel or in an extruder depending on the type of monomer, but usually a method of bulk ring-opening polymerization in the polymerization vessel should be adopted. Is preferred. For example, when glycolide is heated, it melts and becomes liquid, but when heating is continued and ring-opening polymerization is performed, a polymer is produced. When the polymerization temperature is lower than the crystallization temperature of the polymer, the polymer is precipitated during the polymerization, and a solid polymer is finally obtained. The polymerization time varies depending on the ring-opening polymerization method, the polymerization temperature, etc., but in the ring-opening polymerization method in the container, it is usually 10 minutes to 100 hours, preferably 30 minutes to 50 hours, more preferably 1 to 30 hours. is there. The polymerization conversion rate is usually 95% or more, preferably 98% or more, more preferably 99% or more. In order to reduce the residue of unreacted monomers and increase production efficiency, full conversion can be performed. Most preferred.

  Therefore, in the present invention, after adding water to the purified cyclic ester to adjust the total proton concentration in the cyclic ester, the cyclic ester is heated and melted in the presence of a catalyst, and then the molten cyclic ester is opened. It is preferable to employ a method of ring polymerization. This polymerization method is a massive ring-opening polymerization method. The ring-opening polymerization of the cyclic ester in the molten state can be carried out batchwise or continuously using a reaction vessel, tube type or tower type, or extruder type reaction apparatus.

  Further, according to the present invention, the molten cyclic ester is transferred to a polymerization apparatus having a plurality of tubes (both tubes that can be opened and closed at both ends are also preferably used), and produced by ring-opening polymerization in an airtight state in each tube. A method of depositing a polymer is more preferable. In addition, after the ring-opening polymerization of a cyclic ester in a molten state is allowed to proceed in a reaction vessel equipped with a stirrer, the purified polymer is taken out, once the polymer is cooled and solidified, and then the solid-state polymerization reaction is continued below the melting point of the polymer Is also preferable. These methods can be carried out by either a batch method or a continuous method. In any case, by using a method in which the polymerization temperature is controlled in an airtight state (that is, a reaction system without a gas phase), a polymer having physical properties such as a target molecular weight and melt viscosity can be stably and reproduced. It can be manufactured with good performance.

In the method of the present invention, the melt viscosity measured at a temperature of 240 ° C. and a shear rate of 121 sec ⁻¹ is preferably 50 to 6,000 Pa by ring-opening polymerization of a cyclic ester (for example, glycolide or a cyclic ester containing glycolide as a main component). .Multidot.s, more preferably 100 to 5,000 Pa.s polyglycolic acid can be obtained. Further, according to the method of the present invention, a high molecular weight aliphatic polyester having a weight average molecular weight of preferably 50,000 or more, more preferably 80,000 or more, and particularly preferably 100,000 or more can be produced. The upper limit of the weight average molecular weight is about 500,000.

A carboxyl group blocking agent is blended in the aliphatic polyester produced as described above. As the carboxyl group-capping agent, those known as water resistance improvers for aliphatic polyesters such as polylactic acid (see, for example, Patent Document 5 above) can be generally used. For example, N, N-2 Carbodiimide compounds, including monocarbodiimide and polycarbodiimide compounds such as 2,6-diisopropylphenylcarbodiimide, 2,2'-m-phenylenebis (2-oxazoline), 2,2'-p-phenylenebis (2-oxazoline), 2 , 2-phenyl-2oxazoline, styrene-isopropenyl-2-oxazoline and other oxazoline compounds; 2-methoxy-5,6-dihydro-4H-1,3-oxazine and other oxazine compounds; N-glycidylphthalimide, cyclohex Examples thereof include epoxy compounds such as xene oxide.
Of these, carbodiimide compounds are preferred, and those having particularly high purity provide a water-resistant stabilization effect.

  These carboxyl group-capping agents can be used in combination of two or more as required, and are 0.01 to 10 parts by weight, more preferably 0.05 to 5 parts per 100 parts by weight of aliphatic polyester. It is preferable to mix | blend in the ratio of a weight part, especially 0.1-3 weight part.

  Further, in addition to the above carboxyl group-capping agent, the aliphatic polyester is blended with 0.003 to 3 parts by weight, preferably 0.005 to 1 parts by weight of a heat stabilizer with respect to 100 parts by weight thereof. You can also. As the heat stabilizer, phosphate esters and phosphate alkyl esters having a pentaerythritol skeleton structure are preferably used alone or in combination.

  The above-mentioned carboxyl group-capping agent (and a heat stabilizer that is added as necessary) may be added during the polymerization, but it is preferably blended when pelletizing the aliphatic polyester produced by the polymerization. It can also be added both during the pellet section and during polymerization.

  Hereinafter, the present invention will be described more specifically with reference to synthesis examples, examples, and comparative examples. Analysis methods, measurement methods, calculation methods, etc. are as follows.

(1) Quantitative analysis of impurities:
In 10 ml of high-purity acetone, glycolide obtained by accurately weighing about 1 g and 25 mg of 4-chlorobenzophenone as an internal standard substance were added and sufficiently dissolved. About 1 ml of the solution was collected, and an ethyl ether solution of diazomethane was added to the solution. The recommended amount of addition is until the yellow color of diazomethane remains. 2 μl of the yellow colored solution was injected into a gas chromatograph, and methyl esterified glycolic acid and glycolic acid dimer were quantified based on the area ratio of the internal standard substance and the added amount of glycolide and the internal standard substance.
<Gas chromatography analysis conditions>
Apparatus: Hitachi G-3000
Column: TC-17 (0.25 mmφ × 30 m),
Vaporization chamber temperature: 290 ° C,
Column temperature: After holding at 50 ° C. for 5 minutes, the temperature is raised to 270 ° C. at a heating rate of 20 ° C./min, and held at 270 ° C. for 4 minutes.
Detector: FID (hydrogen flame ionization detector), temperature: 300 ° C.
For lactide, impurities can be quantified by the same method as for glycolide.

(2) Moisture measurement:
Using a Karl Fischer moisture meter with a vaporizer [CA-100 manufactured by Mitsubishi Chemical Co., Ltd. (vaporizer VA-100)], about 2 g of a monomer sample accurately weighed was placed in a vaporizer set at 140 ° C. and heated in advance. . Dry nitrogen gas was allowed to flow from the vaporizer to the Karl Fischer moisture meter at a flow rate of 250 ml / min. After the sample was introduced into the vaporizer, the vaporized water was introduced into the Karl Fischer solution, and the end point was defined as the point when the electrical conductivity dropped to +0.05 μg / S from the background. Regarding the measurement of the moisture of the polymer, the temperature of the vaporizer was set to 220 ° C., and the end point was the time when the electric conductivity dropped to +0.1 μg / S from the background.

(3) Moisture measurement in the monomer dissolution tank:
Dry air was allowed to flow inside the monomer dissolution tank in advance, and the relative humidity of the atmosphere was determined with a hygrometer. The absolute temperature was calculated from the temperature of the atmosphere, and the water content inside the tank was calculated from the absolute temperature and the tank volume.

(4) Calculation method of proton concentration:
The total proton concentration in the cyclic ester is calculated based on the total amount of the hydroxycarboxylic acid compound and water contained in the cyclic ester. The proton concentration (mol%) based on the hydroxycarboxylic acid compound is calculated based on the content, molecular weight, and number of hydroxyl groups. On the other hand, the proton concentration based on water is calculated based on the moisture content of impurities contained in the cyclic ester, the moisture content contained in the atmosphere such as the treatment tank, and the total amount and molecular weight of the added water.

Details of the calculation method for Polymer Synthesis Example 1 below are as follows:
<Molecular weight>
The following values were used for the molecular weight of each component in the glycolide (cyclic ester) monomer:
Glycolide: 116.07,
Glycolic acid: 76.05
Glycolic acid dimer: 134.09,
Water: 18.02.

<Proton concentration of impurities in charged monomer>
The impurity concentration (by weight) in the charged glycolide was 50 ppm of glycolic acid, glycolic acid dimer: 360 ppm, and water: 33 ppm. Since the glycolide molecular weight is 116.07, the proton concentration to be given is calculated as follows.
Glycolic acid: 50ppm
116.07 × 50 × 10 ⁻⁶ ÷ 76.05 × 100 = 0.976 mol%
... (i)
Glycolic acid dimer: 360 ppm
116.07 × 360 × 10 ⁻⁶ ÷ 134.09 × 100 = 0.031 mol%
... (ii)
Water: 33ppm
116.07 × 33 × 10 ⁻⁶ ÷ 18.02 × 100 = 0.021 mol%
... (iii)
Total proton concentration given by impurities (i) + (ii) + (iii) = 0.0006 + 0.031 + 0.021 = 0.0596≈0.060 mol% (iv)

<Water in monomer dissolution tank>
The atmosphere in the dissolution tank (volume: 50 liters) after removing as much water as possible by blowing dry air was temperature: 22.5 ° C. and relative humidity: 31%.

From the Chemical Engineering Handbook, the saturated vapor pressure of water at 22.5 ° C. is 2726 Pa, and a relative humidity of 31% corresponds to 2276 × 0.31 = 845.1 Pa as an absolute vapor pressure. Standard state (0 ℃ = 273.2K, 1atm = 101325Pa) in (g per 1 m ³⁾ absolute humidity since water corresponds to a volume of 22.4 l = 0.0224m ³ of 1 mol (18.02 g) as,
18.02 × (845.1 / 101325) × 1 / (0.0224 × (273.2 + 22.5) /273.2)
= 0.00794 × 845.1 / (1 + 0.0366 × 22.5)
= 6.199≈6.2 g / m ³ (Note that this absolute humidity can also be obtained by direct measurement with a “HMI 41T” manufactured by VASALA, for example.)

The amount of water in the dissolution tank having an internal volume of 56 liters was 6.2 × 0.056 = 0.347 g. For 2,500 g (= 194.0 mol) of glycolide monomer charged later,
0.347 / 22500 × 10 ⁶ = 15 ppm
(0.347 / 18.02) ÷ 194 × 100 = 0.010 mol% (v)
<Additive water>
Add 3.85 g of water. For 22,500 g (= 194.0 mol) of glycolide monomer,
3.85 / 22500 × 10 ⁶ = 171.11 ppm
(3.85 / 18.02) ÷ 194 × 100 = 0.110 mol% (vi)
<Total proton concentration>
(Iv) + (v) + (vi) = 0.060 + 0.010 + 0.110 = 0.180 mol%,

  In addition, after adding glycolide to the monomer dissolution tank, adding additional water and heating to become uniform, a part was sampled and charged based on the result of analyzing impurities (water, glycolic acid, glycolic acid dimer) The total proton concentration in the glyceride after dissolution was in good agreement with the total proton concentration calculated from the glycolide impurities (water, glycolic acid, glycolic acid dimer) and the amount of added water before charging.

(5) Melt viscosity:
The polymer sample was placed in a drier at 120 ° C. and contacted with dry air to reduce the water content to 100 ppm or less. Then, it fully dried with the dryer. The melt viscosity was measured using a Toyo Seiki Capillograph 1-C equipped with a capillary (1 mmφ × 10 mmL). About 20 g of a sample was introduced into an apparatus heated to a set temperature of 240 ° C., and held for 5 minutes, and then the melt viscosity at a shear rate of 121 sec ⁻¹ was measured.

(6) Color tone:
Using a TC-1800 manufactured by Sokkyo Denshi Technical Center, measurement was performed by a reflected light measurement method under the conditions of standard light C, 2 ° visual field, and color system. The apparatus was calibrated with a standard white plate (No. 88417). The measurement is carried out three times by packing the pulverized product sample closely so that fine powder does not enter a special petri dish (diameter 3 cm, height 1.3 cm), placing it on the measurement stage, changing the position of the sample, and averaging the values. Was calculated. As the color tone, a YI (yellow index) value indicating yellowness was used.

(7) Molecular weight measurement:
In order to dissolve the polymer sample in the solvent used for molecular weight measurement, an amorphous polymer is obtained. That is, about 5 g of a sufficiently dried polymer was sandwiched between aluminum plates, placed on a 275 ° C. heat press machine and heated for 90 seconds, and then pressurized at 2 MPa for 60 seconds. After that, it was immediately cooled in ice water. In this way, a transparent amorphous press sheet was produced.

A 10 mg sample was cut out from the press sheet produced by the above operation, and this sample was dissolved in a hexafluoroisopropanol (HFIP) solution in which 5 mM sodium trifluoroacetate was dissolved to form a 10 ml solution. The sample solution was filtered through a membrane filter, then injected into a gel permeation chromatography (GPC) apparatus, and the molecular weight was measured. The sample was injected into the GPC apparatus within 30 minutes after dissolution.
<GPC measurement conditions>
Apparatus: Shimazu LC-9A,
Column: HFIP-806M, 2 (series connection) pre-column,
Column temperature: 40 ° C
Eluent: HFIP solution in which 5 mM sodium trifluoroacetate is dissolved,
Flow rate: 1 ml / min,
Detector: RI (Refractive Index: differential refractometer)
Molecular weight calibration: Five standard PMMA species with different molecular weights were used.

(8) Carboxyl group determination About 0.3 g of sample is precisely weighed from a press sheet prepared in the same manner as the sample for molecular weight measurement, and completely dissolved in 10 ml of special grade dimethyl sulfoxide in an oil bath at 150 ° C over about 3 minutes. To do. After adding a few drops of indicator (bromothymol blue / alcohol solution) to the solution, 0.02N sodium hydroxide / benzyl alcohol solution was added, and the color of the solution changed from yellow to green visually. The point was the end point. The carboxyl group concentration was calculated from the dripping amount at that time.

(9) Water resistance evaluation The pellets were sufficiently dried with 120 ° C dry air, placed on a 250 ° C heat press, heated for 3 minutes, and then pressurized at 8 MPa for 1 minute. After that, it was immediately transferred to a press machine in which water was circulated, pressurized to 5 MPa, held for about 5 minutes, cooled, and a transparent amorphous press sheet was prepared.

  The press sheet created by the above operation is cut out to a certain size, fixed to a frame, put in a dryer heated to 70 ° C., heated, and after 1 minute, air is blown so that the area is 10-15 times larger. Stretched. This film was heat-treated at 200 ° C. for 1 minute under tension.

  About 10 mg of the film-like sample produced by the above operation was cut out, placed in a constant temperature and humidity chamber maintained at a temperature of 80 ° C. and a relative humidity of 95%, and left for a predetermined time. After taking out after a predetermined time, the molecular weight of the sample was measured by GPC.

  The degree of polymerization was calculated from the obtained number average molecular weight value, the reciprocal of the degree of polymerization was plotted logarithmically with respect to the exposure time, and the slope of the approximate straight line of the plot was taken as the hydrolysis rate constant.

(10) Carbodiimide purity determination N, N-2,6-diisopropylphenylcarbodiimide in which about 50 mg is precisely weighed is completely dissolved in 10 ml of high-purity acetone. 2 μl of the solution was sampled and injected into a gas chromatograph, and measurement was performed. Calculation was based on the ratio of the area of the main peak of N, N-2,6-diisopropylphenylcarbodiimide to the total peak area excluding the solvent-derived peak.
<Gas chromatography analysis conditions>
Device: Shimadzu GC-14A
Column: TC-17 0.25mmφ × 30m
Vaporization chamber temperature: 290 ° C
Column temperature: held at 150 ° C. for 5 minutes, then heated to 270 ° C. at 20 ° C./minute, held at 270 ° C. for 6 minutes Detector: FID (hydrogen flame ionization detector) Temperature: 300 ° C.

[Monomer Synthesis Example 1]
A 70 wt% glycolic acid aqueous solution is charged in a jacketed stirring tank (also called “reaction can”), and the liquid in the can is heated to 200 ° C. by circulating heat medium oil in the jacket while stirring at normal pressure. Then, the condensation reaction was carried out while distilling the produced water out of the system. Next, while maintaining the can internal solution at 200 ° C., while reducing the internal pressure of the can to 3 kPa stepwise, low-boiling substances such as produced water and unreacted raw materials were distilled off to obtain a glycolic acid oligomer.

  The glycolic acid oligomer prepared above was charged into a stirred tank equipped with a jacket made of SUS304, diethylene glycol dibutyl ether was added as a solvent, and polyethylene glycol was further added as a solubilizer. A mixture of the glycolic acid oligomer and the solvent was subjected to a depolymerization reaction under heating and reduced pressure to co-distill the produced glycolide and the solvent. The distillate was condensed with a double-tube condenser in which hot water was circulated. The condensate was received in a room temperature receiver. In order to keep the amount of solvent in the reaction solution constant, a solvent corresponding to the amount of distilled solvent was continuously supplied to the reaction vessel.

  The reaction was continued and the mixture of glycolide and solvent was distilled off and condensed. The glycolide precipitated from the condensate was separated into solid and liquid, recrystallized with 2-propanol, and then dried under reduced pressure. The purity of glycolide measured by a differential scanning calorimeter (DSC) was 99.99%.

[Monomer Synthesis Example 2]
A condensate was obtained in the same manner as in Synthesis Example 1 except that the solubilizer was changed from polyethylene glycol to octyltetratriethylene glycol. The condensate was received in a receiver in which warm water was circulated through the jacket. The condensate in the receiver was separated into two liquids, the upper layer being a solvent and the lower layer being a glycolide liquid. If the depolymerization reaction is continued after the two-component layer is formed and the co-distillation is continued, glycolide cooled by the condenser passes through the solvent layer as droplets and is condensed in the lower glycolide layer. It was. In order to keep the amount of solvent in the reaction solution constant, the upper solvent layer was continuously returned to the reaction vessel. The pressure in the reaction system was temporarily returned to normal pressure, liquid glycolide was extracted from the bottom of the receiver, the pressure was restored to the original level, and the depolymerization reaction was continued. This operation was repeated several times.

  Furthermore, in Synthesis Example 1, glycolide recovered from the depolymerization reaction system was purified by recrystallization, whereas it was purified using a tower-type purification apparatus. After depolymerization, the crude glycolide crystals separated into solid and liquid were continuously charged at a constant rate into the raw material crystal charging port provided at the bottom of the tower-type purification apparatus. The glycolide was stirred while being raised with a stirring device mounted inside a tower-type purification device, and purified by countercurrent contact between the descending melt of the purified crystal component and the rising crude glycolide crystal in the purification device. Crystals after purification were continuously taken out at a constant rate from an outlet provided in the upper part of the purification apparatus. The recovered purified glycolide had a purity of 99.99% or more as determined by DSC measurement.

[Polymer Synthesis Example 1] Production Example of PGA Sample A Glycolide produced in Synthesis Example 1 (50 ppm glycolic acid, glycolic acid) in a 56 liter SUS container (melting tank) equipped with a steam jacket structure and a stirrer Dimer 360 ppm, water 33 ppm, and therefore total impurity proton concentration 0.060 mol%) 22,500 g, tin dichloride dihydrate 0.068 g (30 ppm), and water 3.85 g [moisture contained in the atmosphere in the container (Considering 0.34 g of moisture)] was added to adjust the total proton concentration (set proton concentration) to 0.18 mol%.

The vessel was sealed, and steam was circulated through the jacket while stirring, and the contents were heated until the temperature reached 100 ° C. This content melted during heating and became a uniform liquid. While maintaining the temperature of the contents at 100 ° C., the contents were transferred to an apparatus consisting of a metal (SUS304) tube having an inner diameter of 24 mm. This device consists of a main body where the pipe is installed and upper and lower plates made of metal (SUS304). Both the main body and the upper and lower plates have a jacket structure, and the heat medium oil is circulated through the jacket part. It has become. When the contents were transferred to the apparatus, a lower plate was attached. When the transfer was finished in each tube, the upper plate was immediately attached. A heat medium oil of 170 ° C. was circulated through the main body and the jacket portions of the upper and lower plates, and held for 7 hours. After a predetermined time, the polymerization apparatus was cooled by cooling the heat medium oil circulating in the jacket. After cooling to near room temperature, the lower plate was removed, and the resulting polyglycolic acid mass was taken out. According to this polymerization method, the yield is almost 100%. The lump was pulverized by a pulverizer to obtain PGA sample A.
Sample A contained water 34 ppm, the weight average molecular weight (Mw) was 193,000, the melt viscosity (MV) was 2690 Pa · s, and the yellowness (YI) was 11.
[Polymer synthesis example 2] PGA sample B production example

Using 2,500 g of glycolide prepared in Monomer Synthesis Example 2 (glycolic acid 70 ppm, glycolic acid dimer 420 ppm, water 10 ppm, impurity total proton concentration is 0.053 mol%), total proton concentration (set proton concentration) 0.22 mol The PGA sample B was obtained in the same manner as in Polymer Synthesis Example 1 except that 5.54 g of water (in consideration of 0.27 g of moisture (humidity) contained in the atmosphere in the container) was added to adjust the content to 5%. It was.
Sample B contained 35 ppm of water, Mw was 184000, MV was 2200 Pa · s, and yellowness (YI) was 8.7.

[Polymer synthesis example 3] PGA sample C production example In order to adjust the total proton concentration (set proton concentration) to 0.32 mol%, 11.5 g of water (considering 0.4 g of water (humidity) contained in the container) was added. A PGA sample C was obtained in the same manner as in Polymer Synthesis Example 2 except that.
Sample C contained 30 ppm of water, Mw was 154000, MV was 1100 Pa · s, and yellowness (YI) was 6.2.

[Polymer Synthesis Example 4] PGA Sample D Production Example As a monomer, 21,375 g of glycolide produced in Synthesis Example 2 (glycolic acid 60 ppm, glycolic acid dimer 460 ppm, water 21 ppm, and thus the total proton concentration of impurities is 0.063 mol%) And L-lactide 1,125 g (lactic acid 0 ppm, lactic acid dimer 270 ppm, water 8 ppm, impurity total proton concentration is 0.030 mol%) to adjust the total proton concentration (set proton concentration) to 0.18 mol% 3.85 g of water (considering 0.27 g of moisture (humidity) contained in the atmosphere in the container) was added, and heat medium oil was circulated through the jacket of the polymerization apparatus at 170 ° C., and the temperature of the upper and lower plates was set to 170 ° C. The procedure was the same as in Synthesis Example 1 except that the temperature was kept and kept for 24 hours. After completion of the polymerization, the yield of the resulting poly (glycolic acid / L-lactic acid) copolymer mass was almost 100%. This lump was pulverized by a pulverizer to obtain PGA sample D.
Sample D contained 25 ppm of water, Mw was 181000, MV was 2300 Pa · s, and yellowness (YI) was 18.

Examples and Comparative Examples (Examples 1-4 and Comparative Examples 1 and 2)
1 part by weight each of N, N-2,6-diisopropylphenylcarbodiimide (CDI-A, CDI-B) having different purity is blended with 100 parts by weight of PGA sample A produced in sufficiently dry polymer synthesis example 1. Then, pellets were obtained while melt kneading using a small twin screw extruder. Extrusion was performed at two temperatures. The pellets obtained without adding N, N-2,6-diisopropylphenylcarbodiimide were referred to as Comparative Examples 1 and 2.
Extrusion conditions Extruder: Toyo Seiki Seisakusho LT-20
Temperature condition: Condition-1: Maximum temperature 240 ° C
Condition-2: Maximum temperature 280 ° C
A film for water resistance evaluation was formed from each pellet.
Table 1 shows the physical properties of the obtained pellets and film.

(Example 5-10 and Comparative Example 3-5)
With respect to 100 parts by weight of the PGA sample A produced in the sufficiently dry polymer synthesis example 1, Adeka Stub PEP-8 (Asahi Denka Kogyo Co., Ltd. cyclic neopentanetetraylbis (octadecyl phosphite)) or Adeka Stab AX-71 (Mono- and di-stearyl acid phosphate manufactured by Asahi Denka Kogyo Co., Ltd.) 0.03 parts by weight, N, N-2,6-diisopropylphenylcarbodiimide (CDI-A, CDI-B, CDI-C) having different purity The same procedure as in Example 1 was conducted except that 1 part by weight of each was blended and the maximum temperature of the extruder was 240 ° C. (condition-1). In addition, the thing which does not add N, N-2,6-diisopropylphenyl carbodiimide was set to Comparative Example 3-5.
Table 2 shows the physical properties of the pellets and film.

(Examples 11-16 and Comparative Example 6)
0.03 part by weight of ADK STAB PEP-8 (Asahi Denka Kogyo Co., Ltd., cyclic neopentanetetraylbis (octadecyl phosphite)) with respect to 100 parts by weight of PGA sample B produced in sufficiently dry polymer synthesis example 2. Example 1 except that 0.1 to 5 parts by weight of N, N-2,6-diisopropylphenylcarbodiimide (CDI-B) was blended and the maximum temperature of the extruder was 240 ° C. (condition-1). Went to. In addition, the thing which does not add N, N-2,6-diisopropylphenyl carbodiimide was made into the comparative example 6.
Table 3 shows the physical properties of the pellets and film.

(Examples 17 and 18 and Comparative Examples 7 and 8)
With respect to 100 parts by weight of the PGA sample C produced in the sufficiently synthesized polymer synthesis example 3, Adeka Stub PEP-8 (Asahi Denka Kogyo Co., Ltd. cyclic neopentanetetrayl bis (octadecyl phosphite)) or Adeka Stab AX-71 ( Asahi Denka Kogyo Co., Ltd. Mono and Di-stearyl Acid Phosphate) 0.03 parts by weight, N, N-2,6-diisopropylphenylcarbodiimide having different purity and 1 part by weight of each blended, the maximum temperature of the extruder is 240 The same procedure as in Example 1 was performed except that the temperature was changed to ° C. (Condition-1). Comparative examples 7 and 8 were prepared without adding N, N-2,6-diisopropylphenylcarbodiimide.
Table 4 shows the physical properties of the pellets and film.

(Examples 19 and 20 and Comparative Example 9)
0.03 part by weight of ADK STAB PEP-8 (Asahi Denka Kogyo Co., Ltd. cyclic neopentanetetraylbis (octadecyl phosphite)) with respect to 100 parts by weight of PGA sample A produced in Polymer Synthesis Example 1 which was sufficiently dried. 1 part by weight or 2 parts by weight of N, N-2,6-diisopropylphenylcarbodiimide (CDI-B) was blended, and pellets were obtained while melt kneading using a large twin screw extruder.
Extrusion conditions Extruder: TEM-41SS (40 mmφ) manufactured by Toshiba Machine Co., Ltd.
Screw: same direction L / D = 4.15 rotation speed 40rpm
Temperature condition: Maximum temperature 240 ℃
Extrusion speed: 30kg / h
The obtained pellets were sufficiently dried with 120 ° C. dry air, and a single layer sheet having a thickness of about 100 μm was formed using a single screw extruder.
Extrusion conditions Extruder: Unit Luder PEX-40-24H type (40mmφ)
Screw: Single full flight type L / D = 24, rotation speed 30rpm
Die: T-die temperature condition: Maximum temperature 270 ° C
Extrusion speed: 10kg / h
Thereafter, the obtained sheet was stretched under the following conditions using a biaxial stretching test apparatus (manufactured by Toyo Seiki Co., Ltd.) to produce an amorphous film having a thickness of about 6 μm.
Drawing condition sheet size: 100mm x 100mm
Preheating temperature: 60 ° C
Preheating time: 20 seconds Stretch ratio: 4 × 4 times (length 4 times, width 4 times)

  The obtained film was fixed to a frame and heat-treated at 200 ° C. for 1 minute. The physical properties of the pellets and film are shown in Table-5. In addition, Comparative Example 9 was obtained without adding N, N-2,6-diisopropylphenylcarbodiimide.

(Example 21 and Comparative Example 10)
0.03 part by weight of ADK STAB PEP-8 (Asahi Denka Kogyo Co., Ltd. cyclic neopentanetetraylbis (octadecyl phosphite)) with respect to 100 parts by weight of PGA sample D produced in Polymer Synthesis Example 4 which was sufficiently dried. The same procedure as in Example 1 was conducted except that 1 part by weight of N, N-2,6-diisopropylphenylcarbodiimide was blended and the maximum temperature under the extrusion conditions was set to 230 ° C. using a twin-screw extruder. In addition, Comparative Example 10 was obtained without adding N, N-2,6-diisopropylphenylcarbodiimide.
The physical properties of the pellet and film are shown in Table-6.

(Examples 22-24)
0.03 part by weight of ADK STAB PEP-8 (Asahi Denka Kogyo Co., Ltd., cyclic neopentanetetraylbis (octadecyl phosphite)) with respect to 100 parts by weight of PGA sample B produced in sufficiently dry polymer synthesis example 2. The same operation as in Example 1 was conducted except that 1 part by weight of three types of carbodiimide compounds were blended and the maximum temperature of the extruder was 240 ° C. (Condition-1).
Table 7 shows the physical properties of the pellets and film.

(Examples 25-27)
0.03 part by weight of ADK STAB PEP-8 (Asahi Denka Kogyo Co., Ltd., cyclic neopentanetetraylbis (octadecyl phosphite)) with respect to 100 parts by weight of PGA sample B produced in sufficiently dry polymer synthesis example 2. The same procedure as in Example 1 was performed except that 1 part by weight of two types of epoxy compounds was blended and the maximum temperature of the extruder was 240 ° C. (condition-1).
The physical properties of the pellets and film are shown in Table-8.

(Examples 28-32 and Comparative Example 11)
0.03 part by weight of ADK STAB PEP-8 (Asahi Denka Kogyo Co., Ltd. cyclic neopentanetetraylbis (octadecyl phosphite)) with respect to 100 parts by weight of PGA sample A produced in Polymer Synthesis Example 1 which was sufficiently dried. The same operation as in Example 1 was performed except that 0.3 to 1 part by weight of five types of epoxy compounds were blended and the maximum temperature of the extruder was changed to 250 ° C. In addition, the thing which does not add an epoxy compound was made into the comparative example 11.
Table 9 shows the physical properties of the pellets and the film.

Industrial available last name

  As for the result of said Table 1-Table 9, all are carboxyl group-capping agents to the aliphatic polyester obtained by the ring-opening polymerization of the cyclic ester which contains water positively as an initiator or / and molecular weight regulator according to this invention. It is confirmed that the carboxylic acid concentration of the resulting aliphatic polyester and the hydrolysis rate of the film obtained therefrom are effectively reduced, that is, an aliphatic polyester having improved water resistance is produced. Show.

Claims (9)

A cyclic ester containing a proton source compound containing water exceeding 80 ppm as an initiator or / and a molecular weight regulator includes water in the cyclic ester and a free α-hydroxycarboxylic acid corresponding to the cyclic ester and a dimer thereof. Ring-opening polymerization was carried out so as to give an aliphatic polyester having a desired molecular weight by changing the amount of water so that the total proton concentration was in the range of more than 0.09 mol% and less than 2.0 mol% , and the resulting aliphatic The manufacturing method of aliphatic polyester characterized by mix | blending a carboxyl group sealing agent with polyester. The production method according to claim 1, wherein the carboxyl group-capping agent is selected from the group consisting of monocarbodiimide, polycarbodiimide, oxazoline, oxazine and an epoxy compound. The production method according to claim 1, wherein the carboxyl group-capping agent is monocarbodiimide. The production method according to any one of claims 1 to 3, wherein water is added to a purified cyclic ester having a water content of 60 ppm or less to adjust the total proton concentration containing water exceeding 80 ppm. The production method according to any one of claims 1 to 4 , wherein the cyclic ester is glycolide alone or a mixture of 60% by weight or more of glycolide and 40% by weight or less of another cyclic monomer capable of ring-opening copolymerization with glycolide. After adjusting the total proton concentration in the cyclic ester, the cyclic ester is heated and melted in the presence of a catalyst, then any one of claims 1 to 5 to deposit the resulting polymer by ring-opening polymerization of cyclic ester in a molten state The manufacturing method as described in. After adjusting the total proton concentration in the cyclic ester, the cyclic ester is heated and melted in a melting tank in the presence of a catalyst, and then the molten cyclic ester is transferred to a polymerization apparatus having a plurality of tubes. The production method according to claim 6 , wherein the polymer is precipitated by ring-opening polymerization in a sealed state. The manufacturing method according to claim 7 , wherein the plurality of tubes of the polymerization apparatus are tubes whose both ends can be opened and closed. After adjusting the total proton concentration in the cyclic ester, the cyclic ester is heated and melted in a melting tank in the presence of a catalyst, and then the molten cyclic ester is allowed to proceed to ring-opening polymerization in a reactor equipped with a stirrer. The production method according to claim 6 , wherein the purified polymer is taken out, the polymer is once cooled and solidified, and then the solid-state polymerization reaction is continued below the melting point of the polymer.

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